The present invention relates to a valve rotator and more particularly to a rotator for a valve in an internal combustion engine, particularly a diesel engine. Such devices are also finding increasing use in spark ignited engines.
Valve rotators for rotating internal combustion engine valves achieve two purposes. The first of these is to rotate the valve, particularly exhaust valves, so that the hot exhaust gases directly impinge on a different portion of the valve face on each stroke. This minimizes burning of the valve and consequent loss of compression, and extends the lift of the valve and valve seat. Whereas it was not uncommon to rebuild diesel engines after 75,000-100,000 miles of use, the current demand is that the engine should not require rebuilding for any reason prior to 300,000 miles of use. The use of valve rotators aids in the achievement of improved engine life through their beneficial effect on the valves and valve seats.
Typical examples of prior art valve rotators which rotate the valves on the valve opening stroke will be found in the patent to Updike U.S. Pat. No. 4,094,280, the patents to Tauschek U.S. Pat. Nos. 3,952,713, 4,003,353, and 4,075,987, the patent to Orent U.S. Pat. No. 3,537,325, the patents to Norton U.S. Pat. Nos. 2,516,795 and 2,761,434, and the patent to Thorne U.S. Pat. No. 2,624,323.
Another type of valve rotator is utilized not only for the purpose of presenting a different surface for the hot gases upon each cycle, but also for the purpose of cleaning the valve seat by effecting rotation of the valve face against the seat at the time of closing. These rotators operate upon the valve closing stroke and wipe deposits, such as carbon deposits away from the valve seat to be blown out of the combustion chamber by the rush of exhaust gases, for example, or by the in-rush of fuel air mixture.
An example of a valve rotator which operates on the valve closing stroke is shown in the patent to May U.S. Pat. No. 3,710,768.
Other references of interest in the field of valve rotators include the patents to Schonlau U.S. Pat. No. 3,890,943, Enke U.S. Pat. No. 3,717,133 Dooley U.S. Pat. No. 2,935,058, Geer U.S. Pat. No. 2,827,886 and Newton U.S. Pat. No. 2,582,060. Lash adjusters which cause valve rotation in both directions (clockwise and counterclockwise) are shown by Leake U.S. Pat. No. 2,875,740. Witzky U.S. Pat. No. 2,775,232 shows a different type of device utilizing an offset rocker arm. Sward U.S. Pat. No. 2,662,511 shows a combined rotator and lash adjuster.
It will be observed from a review of the prior art structures that each is characterized by basic elements including a rotator body, a rotator cap, shiftable element or elements which coact between the cap and the body, and, with the exception of the lash adjusters, a spring washer, e.g., a Belleville washer. The valve spring is usually seated with one of its ends in engagement with the rotator cap. The rotator body usually rests on the cylinder head. The shiftable elements may be either a side loaded coil type garter spring, or a series of steel balls carried in individual circumferentially extending pockets each having a sloping ramp along which the balls move. To bias the balls toward the upper end of the ramp there are provided individual coil springs. The balls project above the surface of the rotator body at each position along the ramp for contact with the spring washer. The spring washers in such prior art devices are arranged so that one peripheral edge of the washer is in contact with the cap, and the other peripheral edge is normally in contact with the body of the rotator. The ball raceway is located between the peripheral edges of the spring washer.
As the load is increased on the balls by increasing the valve spring load during opening of the valve with a rocker arm, the rotator cap is moved toward the rotator body and the balls forced down the ramps overcoming the bias of the coil springs. Movement of the balls down the ramp causes the spring washer to rotate relative to the frictionally held rotator body. Movement of the washer about the valve axis transmits a rotatory motion to the cap with which it is frictionally engaged. The valve spring which is seated against a retainer near the distal extremity of the valve is rotated because of its frictional engagement with the rotator cap. The rotational movement of the valve spring is transmitted to the valve through the retainer which is locked to the valve stem. When the valve reseats, it is in a different angular position from what it was when the cycle began. Valve rotators, as distinct from lash adjusters, effect a net positive rotation in a predetermined direction during the valve opening and closing cycle. To achieve net positive rotation in one direction a, one way clutch system is utilized to inhibit counter-rotation. In these valve opening rotators, the rotator body and rotator cap are located on opposite sides of the spring washer.
The patent to May, supra, explains the operation of a device which operates on the valve closing stroke. In FIGS. 1 and 2 are shown commercial structures which operate on the valve closing stroke and which are characterized by a plurality of spring washers, and a bearing race. In these valve closing rotators, the rotator body and rotator cap are located on the same side of the spring washer.
It is a primary object of the present invention to simplify the prior art structures operable on the valve closing stroke, and particularly those shown in FIGS. 1 and 2, by eliminating parts and to make them less expensive to manufacture. The improved structures hereof can also have a smaller axial dimension, and are less susceptible to fouling by dirt. To achieve these ends a rotator body having a structure like that normally used in the fabrication of a valve rotator operable during the opening stroke may be modified by the provision therein of a "fulcrum". The fulcrum transfers the valve spring load normally proceeding from the cap through the spring washer and the shiftable element or elements to the body of the rotator, to a condition where the load proceeds from the cap to the spring washer and directly to the body. The load is thus relieved from the shiftable element or elements and the cap and body frictionally clutched against relative rotation by the spring washer. Release from the load on the shiftable element or elements allows the shiftable means to "shift" to a different position relative to the cap and body parts (for example, the balls are forced up the ramp). When the valve spring load is reapplied to the shiftable means from the spring washer as the cap and body move relatively apart, and the spring washer comes off the "fulcrum", the shiftable means is contacted thereby under a heavy load and is displaced in the opposite direction (for example, the balls are forced down the ramp). This causes declutching of the cap and body and enables relative rotation between the cap and the body as will be hereinafter more particularly described.
The provision of means for releasing the load on the shiftable element or elements during a valve stroke to enable such element or elements to assume a different position, distinguishes the present invention from the prior art.